Rice gruel is made by boiling rice in water around 100° C. for 30 minutes. It is known that 103˜104 CFU/g of microorganism lives on the surface of rice. Although the microorganism cells are usually killed during the cooking process, heat resistant spores are not completely killed. If people eat homemade or mass produced rice gruel on the spot (or at least within one day), those thermoduric microorganism would not be a serious problem. However, when mass produced rice gruel products are to be stored at room temperature for an extended period of time or distributed, the thermoduric microorganism is easily proliferated. Therefore, traditional methods for preparing rice gruel are not appropriate for the long-term storage.
Techniques for manufacturing ready-to-eat rice products in aseptic packages were introduced in Patent application Nos. 1995-0055582 and 1992-0025931, and the Patent registration No. 228509. For instance, rice was instantaneously sterilized at 135-140° C. for 40-100 seconds five to ten times, or rice was first steam heated at 80-110° C. for 15-25 minutes and added to ultraviolet sterilized deoxidized material, or rice went through a heat treatment at 100-121° C. for 20-40 minutes and was pressure cooked at 140-160° C. for 5-10 seconds twice to ten times.
However, all of the above techniques concern rice in aseptic packages, and it has not been disclosed a process for preparing rice gruel, which is much different from rice, in aseptic package.
Typically, to cook boiled (or steamed) rice, a cup of rice is boiled in 1.1-1.3 cups of water. Meanwhile, to cook rice gruel for patients or for other reasons, a cup of rice is boiled in 4-8 cups of water. Since more water is required to cook rice gruel, microorganism proliferates more easily in rice gruel, and it is very difficult to get the best taste and texture of rice because grains of rice in the rice gruel are spread greatly.
Therefore, there is a need for a simple and effective method for preserving the mild taste and texture of freshly prepared rice gruel, while protecting against microbial contamination.
Particularly, the present inventors tried to develop a process for preparing rice gruel in an aseptic package, featuring proper levels of spreadability and viscosity of grains, excellent texture and safety from microbial contamination.